Methicillin-Resistant Staphylococcus aureus (MRSA) is a major pathogen responsible for serious hospital infections worldwide. These bacteria are resistant to all β-lactam antibiotics due to the production of an additional penicillin-binding protein, the PBP2a (about 75 kDa) encoded by the mecA gene, and which shows low affinity for this class of antibiotics. The protein is the target of lactam antibiotics. The two main groups of Staphylococcus aureus are classified as MRSA and MSSA (Methicillin-sensitive Staphylococcus aureus) depending on whether they are resistant or sensitive to antibiotics.